1. Field of the Invention
This invention relates to a mowing and chopping machine comprising at least two rotors, which are rotatable about respective vertical axes, which are spaced apart transversely to the direction of travel of the machine and consist of tooth-carrying discs, which extend in a common horizontal plane and carry cutting rotor teeth, which are pivoted to the disc near its periphery by means of vertical pins and are curved upwardly or downwardly from the plane of the disc or consist each of a plurality of superimposed cutter blades, and at least one fixed backing cutter, which is disposed in the generally triangular space between the flight paths of the rotor teeth of adjacent rotors.
2. Description of the Prior Art
Such a machine is known from EP-A No. 0 116 532. Each tooth-carrying disc carries rotor teeth differing in length at the top and bottom of the disc, respectively, so that the flight paths described by the radially outer ends of the rotor teeth of adjacent rotors overlap without a risk of collisions between the rotor teeth rotating in the same plane. The arrangement of adjacent rotors close to each other affords the advantage that no strips of uncut plants will be left on the field. Two rotor teeth which are carried by each disc near its periphery consist of pairs of teeth which extend above and below the plane of the disc, respectively, and are pivoted about a common pin, which is fixed in the disc, so that said rotor teeth are movable to a position in which they protrude from the periphery of the disc. But that arrangement involves the danger that when the pin has become worn the rotor teeth may tilt upwardly or downwardly from the plane of the disc and the outer ends of rotor teeth which are curved upwardly and downwardly from the plane of the disc may collide although the flight paths of said outer ends were initially spaced apart. When the revolving rotor teeth strike against an obstacle, they can perform a relatively large angular movement about the axis of the pin toward the axis of the rotor because such angular movement is hardly limited. Finally, the crop material which has been cut off is not sufficiently chopped because the backing cutters do not sufficiently extend into the triangular space between the flight paths of the rotor teeth and have only one or, at most, two knife edges even if each rotor tooth consists of a plurality of superimposed cutter blades.
It is known from U.S. Pat. No. 2,968,304 to provide a mowing machine in which all rotor teeth are equal in length and revolve in a common horizontal plane. That machine comprises two outer rotors and an intermediate rotor, which is offset from the outer rotors in the direction of travel. That arrangement increases the dimensions and weight of the machine as well as its power requirement. Another disadvantage resides in that the rotor teeth are not pivoted to the tooth-carrying discs but are rigidly fixed to the discs and extend in radial directions so that the rotor teeth can easily be damaged when they strike against an obstacle.
Each rotor tooth of the known machine described last terminates in a three-pronged fork and fixed backing cutters are provided, which conform to said trident. But in spite of the backing cutters the chopping action is not satisfactory because the backing cutters are secured to the side walls and/or the rear walls of the machine housing so that each backing cutter can cooperate only with one rotor tooth at a time whereas the material to be processed is not acted upon by the teeth of adjacent rotors and by at least one backing cutter in the triangular space. Besides, the material being processed may be jammed between the backing cutters and the rotor teeth, which move only at a small distance from the backing cutters.
Another known machine, which is disclosed in British Patent Specification No. 1,283,550, comprises two juxtaposed rotors, which are spaced a relatively large distance apart and carry rotor teeth, which are not mounted at the periphery of discs lying in a common plane but are mounted on short, flat arms, which are carried by the rotor shafts and disposed on different levels. On the forward and rear sides of the two rotors, backing cutters or scrapers are provided between the two rotors and said backing cutters or scrapers consist each of a double comb so that the rotor teeth revolving on different levels can move between the teeth of the comb. A disadvantage of that known machine resides in the large distance between the rotors and in the fact that a relatively wide web is provided between the teeth of the comb-shaped backing cutters so that uncut material will be left between the rotors unless the crop to be cut has been grown in rows.
Similar remarks are applicable to another known machine, which comprises a plurality of superposed rotor shafts, which are forwardly inclined and carry a plurality of tooth-carrying discs. A backing cutter is associated with the teeth of each disc and is mounted on the inclined front wall of the machine frame (U.S. Pat. No. 4,397,136). The problems arising in machines having widely spaced apart rotors are entirely different because it is not necessary to make sure that the crops are uniformly removed from a field or meadow in the entire width of the machine without leaving strips of uncut crops.